The 29-year-old has scored twice for the Blades this season but has only made one league appearance in 2013.
Porter joined the club from Derby in July 2011 but has been told by manager Danny Wilson to go out and gain some minutes on the pitch.
"It is important for Chris to get games and, hopefully, goals under his belt," Wilson told the club's official website.
"If he does well and comes back to us for the run-in full of confidence, it can only be of benefit and in the meantime he will be in a Shrewsbury team that faces a number of our rivals."
